A cochlear implant hearing-aid device is used to help hearing impaired and deaf ears gain awareness and understanding of sound. Normally, the hearing sense is physiologically provided by allowing sound waves to enter the ear canal and vibrate the eardrum and middle ear bones. The bones create a fluid wave inside the cochlea. In the cochlea, cells in the Organ of Corti transform the fluid wave into an electrical nerve impulse that travels to the brain. Once these signals have arrived at the brain, a person realizes “hearing”.
The physiological cause of deafness in many individuals is the malfunctioning, or non functioning of the Organ of Corti. Cochlear Implants are needed when there is a hearing-loss due to the absence of sensory portions of the cochlea, but when neural elements are remaining. The cochlear implant hearing-aid device serves as a substitute for the cochlea's Organ of Corti and works by aiding in the creation of hearing by converting sound energy into electrical signals and directly stimulating the neural elements of the cochlea. The implant does this by directly electrically stimulating the remaining nerve fibers that, in a normally functioning ear, would be stimulated by the Organ of Corti.
Typically implants employ a thin wire-like electrode that provides the electrical signal output for stimulating the nerves in the inner ear. The electrode is sized and shaped to fit within the cochlea, and includes a plurality of Astud@-like portions capable of delivering discreet signals to the nerves of the inner ear. The electrode is surgically placed in the cochlea. Examples of cochlear implants are disclosed in the Applicants=earlier applications, including Fritsch et al., U.S. patent application Ser. No. 11/451,715, filed Jun. 13, 2006 (Currently Pending)(Published as US Published Application No. US2007/005117 on 4 Jan. 2007; and the patents and references cited therein, all of which are hereby incorporated by reference. An example of an intra-cochlear implant is shown in the Fritsch et al., U.S. Pat. No. 7,650,194, that issued on 19 Jan. 2010, and an example of an extra-cochlear implant is shown in the Applicants=Fritsch et al., U.S. Published Patent Application, No. US2007/005117 A1, published Jan. 4, 2007.
Most cochlear implants are composed of two main components. The first is an external “Speech Processor” that is worn similarly to a conventional hearing aid. This component receives sound energy and converts that energy into electrical signals. It is mainly devised to convert speech sound energy into electrical energy. The Speech Processor transmits that sound through the skin to an internal component known as the “receiver stimulator”. This “receiver stimulator” is commonly referred to as a cochlear implant, and may be an internal implant that includes an electronic housing body portion that is disposed subcutaneously within the tissue near the ear. The receiver-stimulator usually also includes a string or wire like electrode portion that may be implanted internally of the cochlea; (see the '194 patent) or disposed primarily externally of the cochlea (see the Fritsch '117 published application). The body portion of the receiver stimulator receives the electrical signals from a Speech Processor and delivers the electrical impulses into the cochlea via an electrode array.
The receiver-stimulator is implanted surgically within the skull of the patient to be positioned adjacent to, or internally of the patient's cochlea. One surgical trend has been to reduce the impact of surgery on the patient by reducing the size of the incision and tissue exposed during the surgical procedure. Over the last twenty-five years, the incisions and exposure sizes have become smaller and more circumscribed. Presently, a small incision behind the crease of the ear or in the sub-occipital area is used to gain access to the cochlea.
During cochlear implantation surgery, the surgeon must place the stimulating electrode array of the cochlear implant into the cochlea. Initially, the usual microscopic surgical approach creates a “facial recess” window by drilling the bone (FIG. 6) that overlays the cochlea.
Thereafter, the bone overlaying the cochlea is drilled away in order to create an opening into the interior of the cochlea at the turns of the cochlea. This procedure (and the hole formed thereby) is called the cochleostomy.
Once this route of access has been established, the thread-like implant electrode is placed within the interior of the cochlea into the turns of the cochlea. Small grafts of muscle or facia then are packed around the electrode array at the point where the electrode array enters into the interior of the cochlea. The packing seals the cochleostomy site and also slightly stabilizes the electrode array within the cochlea to fix the position of the electrode within the cochlea. Sealing of the cochleosotomy site and securing of the electrode in place are important to prevent migration of the electrode and to prevent fluids from leaking out of the inner ear and for keeping bacteria out. As the position of the electrode within the cochlea significantly impacts the performance of the implant, it is highly desirable to ensure that the implant is properly positioned within the cochlea.
Techniques for sealing the cochleostomy site and securing the electrode include using fascia, Tisseel™ glue, gelfoam, and suture to help maintain the electrode in the desired position. There is a great deal of imprecision in the present technique of sealing the cochleostomy and securing the electrode, as variations occur from surgeon to surgeon and even from surgery to surgery. This imprecision leads to variations in outcome and unwanted electrode movement. An insecure, or imprecise electrode array placement can cause electrode arrays to move away from their intended positions, and cause cochleostomy sites to not seal well.
The consequence of this movement or migration is that sub-ideal or even non-functional electrode positions result. Since the purpose of the electrode is to deliver an electrical charge to a particular set of nerves within the cochlea, it is highly desirable to have the electrode positioned properly adjacent to the nerve group that is intended to be stimulated. Therefore, the movement of the electrode away from its most desirable position adversely impacts the efficiency of the electrical signal transfer between the electrode and the nerve to be stimulated. As such, it would be advantageous to have a better form of stabilization to thereby help to maintain good signal transfer efficiency and thereby provide a better hearing experience for the patient.
The receiver-stimulator includes a proximally disposed body portion that houses the electronics necessary to receive the signals transmitted from the externally disposed speech processor. The proximal body portion is coupled to a relatively distally disposed electrode that has an appearance similar to a “tail” coupled to the body portion “mouse”. The electrode portion includes a proximal end and a distal end. The distal end is inserted through the boney wall of the cochlea, and internally within the turns of a cochlea, or is otherwise coupled to the implanted electrode array.
The surgical step to create the final position for receiving the receiver-stimulator implant is known as “creation of a pocket”. This pocket is a narrow corridor extending through the tissues ending in a closed distal end like the toe of a sock. The receiver-stimulator is then pushed-up distally into the deepest recess of the pocket, to the blunt ending of the pocket, which is the preferred final position of the receiver stimulator implant. The implant is supposed to heal into position and remain at that point where it is placed deep within the patient. The final position of the receiver stimulator implant, which may vary slightly, is behind and above the ear under the skin.
Unfortunately, the receiver stimulator cannot be secured within the pocket with traditional suture “ties” because it is not reachable when it is placed in the final position in the deepest recess of the pocket. A number of implants that are so placed within pockets will migrate within and out of the pocket. The migration end-point then becomes the permanent position of the receiver-stimulator since the receiver-stimulator heals in place with a scar tissue shell and is immobilized at that point.
The newly migrated receiver-stimulator implant may then be permanently positioned out of position for optimal performance. Most notably, the body portion receiver-stimulator may migrate to a first position low over the ear and interfere with the positioning and retention of the Speech Processor on the ear. The two components (Speech Processor and the body portion of the receiver-stimulator) may also knock against each other causing clicking sounds and disruption of electrical signals. These clicking sounds and electrical signal disruptions can be rather annoying to a patient. The external ear may also be bent in a downward position causing discomfort to the patient.
For the above mentioned reasons, it would be desirable to find a device or method for maintaining the proper positioning of the implanted devices and to limit or eliminate device migration. It is therefore one object of the present invention to provide a device that reduces the likelihood of unwanted movement of the surgically implanted devices after surgery and during the healing process. In particular, it is an object of the present invention to provide a device and method for restricting movement and migration of an intra-cochlear electrode and a receiver stimulator body, to thereby reduce the likelihood of unwanted movement and increase the likelihood that the device will maintain its desired position.